If you have ANY concerns about shooting commercial ammo (the stuff that hundreds of thousands of people have shot MILLIONS and MILLIONS of rounds of in their DCM/CMP/Blue Sky etc. M1 Garands becuase they never heard "expert" say "never shoot any commercial ammo, it will blow up in your rifle etc."), simply buy an adjustable gas screw like this:

OR, if the commerciaL ammo you buy at Cabelas feeds fine, and EJECTS NORMALY the emplty brass approximately at "4: Oclock" and say within 4-10 feet away, you will be fine without the gas screw since that is what the adjustable screw allows you to do , but you save your 35 bucks.

Again, there are several types of commercial ammo that I know don't have any ill effects (Igman, Prvi, Rem Green Box 150 or 165s, Fed. GMM, Amer. Eagle, Black-Hills, etc.). Obviusly, without the gas screw you should not buy any "magnum" or hyper-velocity new types of stuff.

IME, both the Schuster and the McCan adjustable gas plugs are worth the money , even with ammo that's close to USGI milspec . Garand parts prices have exploded over the last 10 years.
Reducing the speed and violence of cycling reduces parts wear and extends brass life. I own one Schuster & 3 McCans.
YMMV.